Photo-electric tube



jam. 16, 19340 T, H NAKKEN PHOTO ELECTRIC TUBE Filed May 27, 1950 R O TN E V W.

THEODOgfIS H. NAKKEN ATTORNEY 7 the aiiinity therebetween without theproduction of a chemical compound.

In practicing my invention, my experiments and deductions have led me tothe belief that the various coatings for my photoelectric tube should belimited to the metals of the first two periodic groups and that it isprobably preferable to associate only two coatings both in the samenumbered periodic series such as barium with cesium and strontium withrubidium, although I contemplate the staging of the coatings as, forexample, the employment of magnesium next the glass and a nextinnercoating of potassium, a second inner coating of rubidium and a thirdinner coating of caesium, by which arrangement in series each coatingwith relation to the next adjacent coating either outer or inner isquite close with relation to its interatomic structure.

Of course, the general object of my invention is to improve in generalboth the method of manufacturing highly efficient photoelectric tubesand to produce photoelectric tubes of the best performance as todurability, dependability and cheapness of manufacture.

The above and further objects of the invention are pointed out moreparticularly in the following claims which are directed to illustrativeembodiments of my invention described in the following specification inconnection with the diagram of the accompanying drawing wherein Fig. lis a sectional view and Fig. 2 is a modification thereof. All thedescriptions, of course, are solely by way of illustration and notlimitation.

In the drawing, a commercial glass bulb A having any usual connection 1to the exhaust system is employed. This bulb is provided with a cathodelead-in 2 and an anode lead-in 3, the

. cathode lead-in 2 preferably having a portion 4. lying physicalh inclose contact with the ex posed inner surface of thebulb A. The lead-in3 is shown serving as a support for the anode 5. The anode lead-in 3 ispreferably shielded from a conductive metal deposit as by a glasstubular extension 6 and by the platform 7, which platform may besupported by glass embedded sup ports 8 and 9.

Connected with one end of the bulb A by means of the throat 10 isanother glass chamber 11 carrying a heat resisting metal capsule 12preferably of molybdenum in which is a charge 13 of the desiredphotoelectric metal or of the chemical compound capable upon heating ofliberating the desired photoelectric metal. It is to be understood thatthe capsule 12 may be multiplied and positioned differently within thechamber 11 or that a. number of chambers 11, each containing itscapsule, may be provided.

In practicing my process, it is preferred that the pill 20 or charge ofmetal or substance performing the coating next to the glass of the bulbA be located on the heat resisting platform '7 preferably of nickel,silver or molybdenum. I have therefore shown in my diagram a physicalseparation between the heat resisting metal which sustains the charge ofmetal to be used as a coating for one coat with respect to another coatand it is, of course, to be understood that this may be multiplied tothe extent that deposited or flash coats are to be employed.

In practicing my invention, after the interior of the bulb A has beenproperly evacuated and after occluded gases have been removed in anyapproved fashion. I subject the platform 7 to a local positioning of ahigh frequency coil to effect a sufficient heating to vaporize the pill20 which effects itsdeposit upon the inner walls of the bulb A. Thispill 20 may be magnesium or barium. The magnesium or barium depositforms a coating in electrical connection with the lead-in part 4 andcompletely covers the interior of the plub except that by the shieldingit fails to contact with the anode lead-in 3. I then preferably burn outthe window B and burn out the interior of the neck 10.

The substance of the material 20, instead of magnesium, may be any oneof the metals of the second periodic group capable of existing in thepure state or in the form of a salt capable of producing the vaporizedmetal when subjected to heat. If it is desired to employ such a metal asexists only in the form of a salt or in some chemical form requiringphysical retaining during the process of heating preliminary tovaporicing, a cartridge like the cartridge 12 may be provided on theplatform 7.

The next preferred step is to effect the local heating of the capsule 12to effect the vaporizing of .a metal or substance forming the metal forthe next inner coating within the bulb A. With ice the first coatingbarium, the charge 13 may well be caesium. The vaporized caesium isdischarged through the throat 10 and condenses upon the magnesium orbarium inner surface coating of the bulb A. Further exhaustion of thebulb may be continued if desired and it is, of course, to be understoodthat the occluded gases within the chamber 11 and the capsule 12 havebeen driven off before flashing the charge within the capsule.

After all the flashings have been accomplished by means of all thechambers 11 that are provided; or by means of all the capsules in asingle chamber 11, the bulb A may be sealed off both at the neck 10 andat the pump tube 1 when it is finished ready for employment.

In some cases it may be preferred that the charge 13 be a mixture ofphotoelectric metals such as potassium, rubidium and caesium, or amixture of the salts of such metals or any two of them which uponheating are capable of producing a vaporized metal. In this procedure,the inner coatings are deposited in admixture and not as superimposedcoatings, but the interrelation as to imprisoning effect is present,nevertheless. Described differently, the caesium on a magnesium base isbetter held against wandering or creeping when mixed with potassium andrubidium and it appears that it does not require that the potassium withrubidium be deposited-in films one under the other.

What I claim and desire to secure by United States Letters Patent is:

1. A photoelectric tube comprising a glass bulb having a cathode lead-inin physical contact with the exposed inner surface of said bulb and ananode lead-in; an inner coating for said bulb of an electricallyconducting metal of the second periodic group in electrical connectionwith said cathode lead-in; an inner exposed coating for said bulb of asensitive photoelectric metal of the first periodic group; and anintermediate coating layer of one of the metals of the first twoperiodic groups which more nearly coincides with the interatomicstructure of both the two aforementioned coatings than does theinteratomic structure of said inner coating approach identity with theinteratomic structure of said first aforementioned coating.

2. A photosensitive device comprising a vac- 43mm: comminer; an mafiathem; am a-mfie w M tmelectflc elements, wan llemji -in extendingconductively from wfltmufis mm mm fish". mwm mifieam fmm the mem- M1 i man wmmm *imim connection with mm wade; mm 3 Q1 by we displacement w m?51 Emma number in the mammals mm mum Wm wmmimr; a, amt-he mm 1222" 5tending from wmmm mm emmmm" gamma mm cmrmectimn with 55mm wthoflm emwmmising an M55 surface flaming xmw wmmmmm K m N.

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